This is a continuation of the study of the mechanisms underlying experimental cerebral edema, by creation of cold injury in adult cats,through quantitative determinations of regional cerebral edema (specific gravity method), regional cerebral blood flow (C-14 antipyrine auto radiography) and brain tissue energy metabolism (Lowry method), with proposal of some additional studies. Studies include measures of vasomotor responses and the effects of terapeutic modalities, specifically corticosteroids and hyperosmolar agents. Studies are now being initiated in regional tissue levels of dopamine, serotonin, norepinephrine and GABA, and histochemical fluorescence techniques for catecholamines will be undertaken in the near future. These on neurotransmitters and putative neurotransmitters will be carried out in cold injury edema, as well as experimental head injury in the rat (concussion) being carried out in collaboration with the Brain Research Laboratory, University of Lund, Lund, Sweden.